The invention relates to a process for producing a laminate comprising individual layers, comprising a sequence of operations in which
first a support substrate is provided, to which
a composition which is flowable under processing conditions is applied as a layer, to which layer
subsequently at least one further composition which is flowable under processing conditions is applied as a layer.
Laminates are multilayer sheetlike materials. Laminates in the form of plasters for application to the skin generally comprise at least one film and at least one pressure sensitively adhering layer. In the context of the invention, the term xe2x80x9claminatexe2x80x9d denotes a structure comprising individual layers, in some cases none of these layers comprising a film. In accordance with the prior art, multilayer laminates are normally produced by joining individual single-ply layers. A layer of this kind is produced by first providing a support substrate, generally in the form of a dehesively treated film, which is then coated with a xe2x80x9cliquidxe2x80x9d, i.e., solvent-containing, polymer composition. Subsequent drying of the coated substrate brings about evaporation of the solvent and, with it, crosslinking of the polymer chains in the applied layer. The dried polymer layer can then be lined with a removable film.
Following the abovementioned operations, a multilayer laminate is produced by joining two or more single-ply layers, the cover film of each individual layer being discarded.
The known production process is disadvantageous in a number of respects. First of all, it is necessary to produce individual layers in a sequence of operations and then to join these layers. Since, moreover, the cover films of each layer are discarded, the process is profligate in its use of materials.
Furthermore, the incorporation of volatile active substances and/or auxiliaries into solvent-containing compositions leads, during the drying of each layer and/or of the laminate, to the evaporation of axe2x80x94in certain instances considerablexe2x80x94fraction of the substances incorporated. Overall, the customary coating process associated with the production of a multilayer laminate is uneconomic and costly, and in some cases even unsuitable, for the majority of the active substances and auxiliaries of this class of substance.
The invention is based on the object of specifying a process for producing a laminate comprising individual layers, which process avoids the abovementioned disadvantages and difficulties, is suitable for an economically advantageous production of laminates comprising pharmaceutical and/or cosmetic ingredients, and minimizes evaporative losses on drying and the consumption of cover film material.
A more particular object of the invention is to provide a process for producing a laminate comprising individual layers, such process including a sequence of operations in which initially a support substrate is provided, to which at least on e composition which is liquid under the processing conditions is applied as a layer.